Propagation of Electromagnetic Waves in the Atmosphere

What are Waves?

The movement of disturbance in a particular medium without the net movement of the particles is known as a wave. There are different types of waves with different characteristics, which are as follows.

Types of waves

Below are the types of waves that we encounter around us. It may be visible in some forms, but mostly it occurs as a phenomenon and is not visible.

Transverse waves

The direction of the movement of particles is at the right angle to the direction of propagation of the wave. The highest and the lowest point in a transverse wave are known as crest and trough, respectively. Some examples of transverse waves are light waves, water waves, and the waves produced by stringed instruments.

Longitudinal waves

The direction of propagation of the wave is always the same as the direction of the movement of particles. When the particles of the medium are closed together, then it is known as the compression, and when the particles of the medium are far apart, it’s known as the rarefaction. Some examples of longitudinal waves are earthquake waves and sound waves. 

Electromagnetic waves

The waves that occur due to the vibrations of both magnetic and electric fields are known as electromagnetic waves. There are many examples of electromagnetic waves, such as X-rays, cosmic waves, light ways, and radio signals.

Mechanical waves

These types of waves require a material medium for their propagation. Sound waves and water waves are great examples of mechanical waves.  

Matter waves

The movement of any type of particle comes under the category of matter waves. Let’s say, for example, you throw a stone in water. The ripples generated due to this are an example of matter waves. 

What are Electromagnetic Waves?

To learn about the propagation of electromagnetic waves in the atmosphere, you first need to learn about the basics. Let’s have a look at the basics of electromagnetic waves. When there are vibrations between the electric field and magnetic field, an electromagnetic wave is generated. 

In a vacuum, electromagnetic waves travel at a speed of 3 x 108 m/s. If the electromagnetic wave is travelling in some or other medium than vacuum, then the speed of electromagnetic waves ought to be less than that of the speed of electromagnetic waves in the vacuum. 

Modes of Propagation of Electromagnetic waves

The electromagnetic waves propagate from the transmitter antenna to the receiver antenna. You will find three modes of propagation of electromagnetic waves. 

Ground waves

When the ground surface is the mode of propagation of the electromagnetic waves, then the waves are known as ground waves. 

Space waves

When there is no reflection and refraction of waves while they are travelling from the transmitter antenna to the receiver antenna, then that type of wave is known as the space wave. 

Sky waves

When the sky is the mode of propagation of electromagnetic waves such that they are reflected back to the earth through the ionosphere, those waves are known as sky waves.

Characteristics of Electromagnetic waves

There are many properties of electromagnetic waves. Some of them are listed below. 

• The electromagnetic waves have the speed of light. 
• No medium is required for the propagation of electromagnetic waves. 
• They show the properties like interference, diffraction, and polarisation. 
• The electrical and magnetic field doesn’t deflect electromagnetic waves. 
• The electromagnetic waves always travel in the form of transverse waves. 

How to Find Direction of Propagation of Electromagnetic Waves

To calculate the direction of propagation of electromagnetic waves, you need to use the right-hand thumb rule. You could also calculate the direction by the cross-product of the electric and magnetic fields. 

Look out for the plane which is perpendicular to both the planes, where the electric field and magnetic field vector lies. That will give you the direction of propagation of Electromagnetic waves. 

Example of Propagation of Electromagnetic wave

For example, you have two vectors A and B, and you need to calculate the direction of propagation of the electromagnetic wave. The cross-product of the A vector and B vector would give you the magnitude of propagation of electromagnetic waves. In comparison, the direction of propagation of electromagnetic waves can be calculated by pointing your thumb to the A vector and the rest of the fingers to the B vector. Then, the curling of your fingers will indicate the direction of propagation of the electromagnetic wave. 

What is the Right-Hand thumb rule?

Whenever you do a cross-product to calculate the direction of propagation of an electromagnetic wave, you need this rule to calculate the direction of propagation of the electromagnetic wave. The process of using the right-hand thumb rule is as follows:

• Open your palm of the right hand.
• Your thumb should be in the direction of the first vector. 
• Your remaining fingers should point to another vector. 
• The curl of your fingers will indicate the direction of propagation of electromagnetic waves.

Conclusion

I hope this article will help you to get clarification of the topic of determining the direction of the propagation of electromagnetic waves in the atmosphere. You must be clear with the topic of waves and their variations. There’s a detailed explanation of electromagnetic waves, their characteristics, and the determination of the direction of these electromagnetic waves.